If it is turned on, you can just click Start->Programs->Accessories->System Tools->System Restore and pick the date you want to roll back to. I have done that a couple of times and it worked out well.
I believe it only changes the Windows directories and possibly your my documents directory. Not sure on that though. I have used it when I installed something that updated a DLL file I didn't want updated. It rolled back to the previous version but didn't remove the directory that the program was installed in so...
Depending on what you want to accomplish, it should work well.
J_K_M_A_N